HLT design help wanted

[Dougal]

Hi all,

I want to upgrade my old HLT (an Agee preserver) to make it a bit more reliable at hitting temperatures, especially since the original thermostat stopped working.  I'm not quite sure how best to do this but from what I read, people use PID controllers. What kind would I need, and what's the deal with SSRs? Do you only need those for holding a consistent boil?

As for the probe, the preserver already has an 8mm well for a thermostat probe inside (see photos). What type of probe do you recommend?

Cheers,

Douglas

 

[Stu H]

Can't help, but I'm interested, being a fellow Agee Preserver user (with the totally inaccurate thermostat!!!).

[Reece]

Hey mate Ive only ever used full programmable PID controllers for flow control, havent used the auto ones for temperature control so I cant really tell you. Maybe they have a better hysteresis than standard temperature controllers? SSR are a movement free version of the standard Electro-Mech relay. When you find out your current draw you will be able to find a suitable relay of any variety doesn't have to be SSR. Once you have your controller it will work with a certain probe like a K type thermocouple or thermistor etc.

[Dougal]

Great, thanks guys.

So I'd be looking at one of these PID controllers, and for the 10A load of the preserver, a 25A SSR and heatsink like this, and then maybe a thermocouple like this that fits inside the preserver's thermowell?

Can you calibrate the PID so that the temperature measured by it is adjusted to match a reference thermometer reading?